Airflow generator

ABSTRACT

The disclosure provides an airflow generator. The airflow generator includes a casing, a fan blade and a muffling part. The casing has an air inlet, an air outlet, an accommodating space and a bypass opening connected to one another. The fan blade is disposed in the accommodating space. The muffling part is located outside the accommodating space and is disposed at the bypass opening. The muffling part has an airflow channel, and the airflow channel is connected to the accommodating space via the bypass opening. The fan blade is capable of sucking ambient air into the accommodating space via the air inlet so as to create an air current throughout the accommodating space and to force the air current to flow into the airflow channel via the bypass opening.

CROSS-REFERENCE TO RELATED APPLICATIONS

This non-provisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No(s). 201810249200.9 filed in China on Mar. 22, 2018 the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION Technical Field of the Invention

The disclosure relates to an airflow generator, more particularly to an airflow generator having a muffling part.

Description of the Related Art

As technology progresses, electronic devices, such as desktop computers, laptop computers or servers have a significant increase in performance, but it comes with a large amount of high-temperature heat. The high-temperature heat will increase the electronic device's running temperature and lower its performance. To prevent this, most of the electronic devices have a fan for heat dissipation.

However, the interaction between the fan blade and the casing would cause a noise called blade passing frequency noise (abbreviated to BPF noise). Some change the shape of the fan blade or the shape of the airflow channel in order to eliminate such noise, but there is still no remarkable improvement.

SUMMARY OF THE INVENTION

One embodiment of the disclosure provides an airflow generator. The airflow generator includes a casing, a fan blade and a muffling part. The casing has an air inlet, an air outlet, an accommodating space and a bypass opening connected to one another. The fan blade is disposed in the accommodating space. The muffling part is located outside the accommodating space and is disposed at the bypass opening. The muffling part has an airflow channel, and the airflow channel is connected to the accommodating space via the bypass opening. The fan blade is capable of sucking ambient air into the accommodating space via the air inlet so as to create an air current throughout the accommodating space and to force the air current to flow into the airflow channel via the bypass opening.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only and thus are not limitative to the present disclosure and wherein:

FIG. 1 is a perspective view of an airflow generator according to a first embodiment of the disclosure;

FIG. 2 is a cross-sectional view of the airflow generator in FIG. 1;

FIG. 3 is a schematic view showing how the muffling part in FIG. 1 reduces noise; and

FIG. 4 is a cross-sectional view of an airflow generator according to a second embodiment of the disclosure.

DETAILED DESCRIPTION

In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It will be apparent, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawing.

In addition, the following embodiments are disclosed by the figures, and some practical details are described in the following paragraphs, but the present disclosure is not limited thereto. Furthermore, for the purpose of illustration, some of the structures and components in the figures are simplified, and wires, reference lines or buses are omitted in some of the figures.

Moreover, the terms used in the present disclosure, such as technical and scientific terms, have its own meanings and can be comprehended by those skilled in the art, unless the terms are additionally defined in the present disclosure. That is, the terms used in the following paragraphs should be read on the meaning commonly used in the related fields and will not be overly explained, unless the terms have a specific meaning in the present disclosure.

Please refer to FIG. 1 and FIG. 2. FIG. 1 is a perspective view of an airflow generator according to a first embodiment of the disclosure. FIG. 2 is a cross-sectional view of the airflow generator in FIG. 1.

This embodiment provides an airflow generator 1. The airflow generator 1 is, for example, a centrifugal fan and can be mounted in an electronic device such as a laptop computer. The airflow generator 1 includes a casing 10, a fan blade 20 and a muffling part 40.

The casing 10 is made of a hard material such as a plastic material. The casing 10 has an air inlet 11, an air outlet 12, an accommodating space 13 and a bypass opening 14 connected to one another. In detail, the casing 10 includes a first plate 15, a second plate 16 and a side wall 17, and the first plate 15 and the second plate 16 are respectively connected to two opposite sides of the side wall 17 so as to form the accommodating space 13 and the air outlet 12 with the side wall 17. The air inlet 11 is located on the first plate 15. The bypass opening 14 is located on the side wall 17. The bypass opening 14 divides the side wall 17 into a first wall section 171 and a second wall section 172. The second wall section 172 includes a connecting portion 1721 and a tongue portion 1722 connected to each other. The connecting portion 1721 is located between and connected to the bypass opening 14 and the tongue portion 1722.

The fan blade 20 is disposed within the accommodating space 13 of the casing 10. From the viewpoint of FIG. 2, the fan blade 20 is able to be rotated in counter clockwise direction. As shown in FIG. 2, the fan blade 20 is able to be rotated along a direction D, and during the rotation, each blade of the fan blade 20 can sequentially pass through the tongue portion 1722, the connecting portion 1721, the bypass opening 14 and the first wall section 171. By this configuration, the fan blade 20 is able to suck ambient air into the accommodating space 13 via the air inlet 11 so as to create an air current throughout the accommodating space 13 and then discharge it via the air outlet 12.

In this embodiment, the muffling part 40 is made of, for example, a hard material such as a plastic material. The muffling part 40 is disposed on the outer surface of the side wall 17 and covers the bypass opening 14. In other words, the muffling part 40 is located outside the accommodating space 13. In detail, the muffling part 40 is a hollow structure which has an airflow channel 41 connected to the bypass opening 14. Thus, the airflow channel 41 is connected to the accommodating space 13 via the bypass opening 14. In more detail, the muffling part 40 includes a longer side plate 42, a shorter side plate 43, an upper plate 45, a lower plate 46 and an end plate 44. The longer side plate 42 includes an extension part 421 and a guiding part 422. The longer side plate 42, the shorter side plate 43, the upper plate 45, the lower plate 46 and the end plate 44 together form the airflow channel 41, and the extension part 421 of the longer side plate 42, the shorter side plate 43, the upper plate 45 and the lower plate 46 are respectively connected to sides of the end plate 44. The guiding part 422 of the longer side plate 42, the shorter side plate 43, the upper plate 45 and the lower plate 46 are respectively connected to edges of the bypass opening 14.

In this embodiment, the guiding part 422 is a curved plate, and the muffling part 40 and the casing 10 have a smooth junction between the guiding part 422 and the connecting portion 1721 of the second wall section 172 that guides air current generated by the fan blade to flow into the airflow channel 41 via the bypass opening 14. This helps to reduce the blade passing frequency noise (abbreviated to BPF noise) caused by the fan blade 20. It is noted that the blade passing frequency noise is mainly caused by the rotor-stator interaction.

Moreover, in this embodiment, the shorter side plate 43 and the first wall section 171 are the same in curvature, thus the shorter side plate 43 can fit on the surface of the first wall section 171. This configuration helps to decrease the overall volume of the airflow generator 1, such that the airflow generator 1 is able to be mounted within a compact laptop computer.

However, the shorter side plate 43 is optional. For example, in some other embodiments, the muffling part may have no shorter side plate, and the airflow channel may be formed by the longer side plate, the first wall section, the upper plate, the lower plate and the end plate.

The science behind the muffling part 40 is described in the following paragraphs.

Please refer to FIG. 3. FIG. 3 is a schematic view showing how the muffling part in FIG. 1 reduces noise. The airflow channel 41 of the muffling part 40 has a length L, and the length L is determined by the ‘blade passing frequency’ of the fan blade 20. When the length L is one fourth of the wavelength λ of the blade passing frequency of the fan blade 20, an incident wave 60 which is formed while the air current flowing into the airflow channel 41 can be reflected by the bottom of the muffling part 40 so as to produce a reflected wave 70 which has the same amplitude but has a phase opposite to the incident wave 60. The incident wave 60 and the reflected wave 70 would interfere with each other, thereby reducing the noise which is caused by the blade passing frequency of the fan blade 20. For example, when the blade passing frequency of the fan blade 20 is 2145 Hz, the wavelength λ of the blade passing frequency of the fan blade 20 is equal to sound speed divided by frequency; that is, 342(m/s)/2145(Hz)=0.16(m). Therefore, the length L of the airflow channel 41 of the muffling part 40 is equal to one fourth of the wavelength λ; that is, 0.16(m)/4=0.04(m).

Then, to compare the airflow generator 1 with one without the muffling part 40. An experiment result shows that the blade passing frequency noise and the total noise of the airflow generator without the muffling part 40 are respectively 35.6 dB(A)/20 u Pa and 43.4 dB(A)/20 u Pa, but those of the airflow generator 1 are respectively decreased to 26.8 dB(A)/20 u Pa and 41.4 dB(A)/20 u Pa. The total noise value means the sum of all the noise that caused by the airflow generator operating at a frequency range between 100 Hz and 20 kHz. Obviously, with the help of the muffling part 40, the airflow generator 1 has a significant effect in reducing noise.

Moreover, the following further discusses the relationship between the position of the muffling part 40 and the effect of the noise reduction. As shown in FIG. 2, a reference line S is defined to pass through the rotating axis R of the fan blade 20 and to be perpendicular to a plane P where the air outlet 12 is located, and the muffling part 40 and the tongue portion 1722 are respectively located at two opposite sides of the reference line S. In such a case, the blade passing frequency noise and the total noise are respectively 26.8 dB(A)/20 u Pa and 41.4 dB(A)/20 u Pa. In another case that the muffling part 40 and the tongue portion 1722 are located at the same side of the reference line S and the muffling part 40 is disposed on the tongue portion 1722, the blade passing frequency noise and the total noise are respectively increased to 39.5 dB(A)/20 u Pa and 44.9 dB(A)/20 u Pa. Therefore, the configuration that the muffling part 40 and the tongue portion 1722 are disposed at opposite sides of the reference line S has a better effect in reducing noise.

In addition, since the muffling part 40 is made of hard material, the reflected wave 70 is ensured to have the same amplitude as the incident wave 60 so as to completely eliminate the incident wave 60.

Furthermore, in some other embodiments, the muffling part may be made of a soft material such as a soft plastic material or a soft rubber material. As such, the muffling part is able to be deformed to change its shape, helping the airflow generator to fit in a laptop computer which has an irregular space.

In this embodiment, the airflow generator 1 further includes a porous member 50 located between the guiding part 422 and the bypass opening 14. The porous member 50 is, for example, a sponge. The porous member 50 is able to reduce the turbulence occurring when the air current hitting a sharp part between the shorter side plate 43 and the first wall section 171 so as to reduce the noise caused by the turbulence. In addition, the porous member 50 has a plurality of pores 51, and the pores 51 help the air current to flow into the muffling part 40 and also help to reduce the blade passing frequency noise.

Another experiment result shows that the total noise caused by the airflow generator 1 is approximately 40 dB(A)/20 u Pa and is smaller than that of the airflow generator without both of the muffling part 40 and the porous member 50 (e.g., 43.4 dB(A)/20 u Pa) and even smaller than that of the airflow generator only having the muffling part 40 (e.g., 41.1 dB(A)/20 u Pa). Obviously, the porous member 50 helps to enhance the effect in reducing noise.

In this embodiment, the muffling part 40 is detachably mounted on the side wall 17 via screws or other fasteners. Therefore, the muffling part 40 can be detached from the casing 10 so that it is more convenient to clean dust therefrom. On the other hand, the fan blade 20 would deform when being used for in a long time, and the deformed fan blade 20 might be replaced with a new fan blade. However, the new fan blade may have a blade passing frequency different from the original fan blade. In this case, the muffling part 40 can be replaced with another muffling part having an airflow channel having a length equal to one fourth of the wavelength of the blade passing frequency of the new fan blade, thereby maintaining the effect of the noise reduction. However, in some other embodiments, the muffling part and the casing may be made of one piece to increase the airtightness level between the muffling part and the casing.

In this embodiment, the muffling part 40 is fixed at the side wall 17, but the present disclosure is not limited thereto. In some other embodiments, the muffling part may be fixed at the first plate or the second plate of the casing.

In addition, the type of the airflow generator 1 is not restricted. In some other embodiments, the airflow generator may be an axial fan.

Furthermore, the present disclosure is not limited to the above muffling part 40. Please refer to FIG. 4. FIG. 4 is a cross-sectional view of an airflow generator according to a second embodiment of the disclosure. This embodiment provides a muffling part 40′ which is a long hollow rectangular tube protruding from a side of a casing 10′ and being connected to an accommodating space 13′ of the casing 10′. The muffling part 40′ has an airflow channel 41′ in a length of L2, and the length L2 equals to one fourth of the wavelength of the blade passing frequency of the fan blade 20′. Similarly, the muffling part 40′ also helps to reduce the noise.

According to the airflow generator as discussed above, since the airflow channel of the muffling part has a length equal to one fourth of the wavelength of the blade passing frequency of the fan blade, the incident wave and the reflected wave occurring while the air current flowing into the airflow channel can interfere with each other so as to reduce the noise caused by the airflow generator.

In addition, the configuration that the muffling part and the tongue portion are disposed at opposite sides of the reference line, which passes through the rotating axis of the fan blade and is perpendicular to a plane where the air outlet is located, has a better effect in effect in reducing noise.

Moreover, the porous member is able to reduce the turbulence occurring when the air current hitting the sharp part between the shorter side plate and the first wall section so as to reduce the noise caused by the turbulence. In addition, the pores of the porous member help the air current to flow into the muffling part and also help to reduce the blade passing frequency noise.

Furthermore, since the muffling part is made of hard material, the reflected wave is ensured to have the same amplitude as the incident wave so as to completely eliminate the incident wave, thereby increasing the effect in reducing noise.

Furthermore, the smooth junction between the guiding part and the connecting portion helps the air current generated by the fan blade to flow into the airflow channel.

In some other embodiment, the muffling part may be made of soft material, such that the muffling part is able to be deformed to change its shape, helping the airflow generator to fit in a laptop computer which has an irregular space.

Also, the muffling part can be detached from the casing, thus it is more convenient to clean dust therefrom. On the other hand, when the fan blade is replaced by a new fan blade, the muffling part is able to be replaced by another muffling part having an airflow channel having a length equal to one fourth of the wavelength of the blade passing frequency of the new fan blade, thereby maintaining the effect of the noise reduction.

The embodiments were chosen and described in order to best explain the principles of the disclosure and its practical applications, to thereby enable others skilled in the art to best utilize the disclosure and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the disclosure be defined by the following claims and their equivalents. 

What is claimed is:
 1. An airflow generator, comprising: a casing having an air inlet, an air outlet, an accommodating space and a bypass opening connected to one another; a fan blade disposed in the accommodating space, and a muffling part located outside the accommodating space and disposed at the bypass opening, the muffling part having an airflow channel, and the airflow channel connected to the accommodating space via the bypass opening; wherein, the fan blade is capable of sucking ambient air into the accommodating space via the air inlet so as to create an air current throughout the accommodating space and to force the air current to flow into the airflow channel via the bypass opening.
 2. The airflow generator according to claim 1, further comprising a porous member, the porous member disposed at the bypass opening and having a plurality of pores connected to the accommodating space and the airflow channel.
 3. The airflow generator according to claim 1, wherein the airflow channel has a length equal to one fourth of a wavelength of a blade passing frequency of the fan blade.
 4. The airflow generator according to claim 1, wherein the casing comprises a first plate, a second plate and a side wall, the first plate and the second plate are respectively connected to two opposite sides of the side wall, the first plate, the second plate and the side wall together form the accommodating space and the air outlet, the air inlet is located on the first plate, the bypass opening is located on the side wall, the bypass opening divides the side wall into a first wall section and a second wall section, the second wall section comprises a connecting portion and a tongue portion connected to each other, the connecting portion is located between and connected to the bypass opening and the tongue portion.
 5. The airflow generator according to claim 4, wherein a reference line is defined to pass through a rotating axis of the fan blade and to be perpendicular to a plane where the air outlet is located, and the bypass opening and the tongue portion are respectively located at two opposite sides of the reference line.
 6. The airflow generator according to claim 1, wherein the muffling part comprises a longer side plate, a shorter side plate, a upper plate, a lower plate and an end plate, the longer side plate comprises an extension part and a guiding part connected to each other, the longer side plate, the shorter side plate, the upper plate, the lower plate and the end plate together form the airflow channel, the extension part of the longer side plate, the shorter side plate, the upper plate and the lower plate are respectively connected to sides of the end plate, and the guiding part of the longer side plate, the shorter side plate, the shorter side plate, the upper plate and the lower plate are respectively connected to edges of the bypass opening.
 7. The airflow generator according to claim 1, wherein the muffling part and the casing are of one piece.
 8. The airflow generator according to claim 1, wherein the muffling part is detachably mounted on the casing.
 9. The airflow generator according to claim 1, wherein the muffling part is a made of a hard material.
 10. The airflow generator according to claim 1, wherein the muffling part is a made of a soft material.
 11. The airflow generator according to claim 1, wherein the porous member is a sponge. 